DNA as Hereditary Material: Key Experiments

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Questions and Answers

What was the primary goal of the experiment conducted by Avery, McCarty, and MacLeod?

To develop a vaccine for S.pneumoniae

To identify which macromolecule was the transforming principle (correct)

To prove that proteins are the genetic material

To observe the effects of heat-killed bacteria on mice

What role did DNase play in the Avery, McCarty, and MacLeod experiment?

It inhibited the growth of S.pneumoniae

It acted as a control for protein digestion

It degraded DNA, confirming its role as hereditary material (correct)

It transformed type II R-strain into type III S-strain

What did the results of the Hershey and Chase experiment indicate?

Both DNA and proteins are essential for viral infection

DNA is the genetic material injected into host cells (correct)

Proteins are more effective than DNA in genetic transfer

Bacteriophages do not require their own genetic material

In the Hershey and Chase experiment, which radioactive isotopes were used to label DNA and proteins, respectively?

35S for proteins and 32P for DNA Signup and view all the answers

What organism was primarily used as a host in the Hershey and Chase experiment?

Escherichia coli Signup and view all the answers

Which conclusion was drawn from the observations of the Avery, McCarty, and MacLeod experiment?

DNA is the genetic material responsible for transformation Signup and view all the answers

What was the common resistance among scientists regarding Avery, McCarty, and MacLeod's findings?

Reluctance to accept DNA as genetic material Signup and view all the answers

How did the experimental designs of the Avery, McCarty, and MacLeod and the Hershey and Chase experiments differ?

One focused on S.pneumoniae while the other focused on E.coli Signup and view all the answers

What did Friedrich Miescher first isolate in 1869?

Nuclein from white blood cell nuclei Signup and view all the answers

Which scientific belief about heredity was prevalent during Miescher’s time?

Proteins were better candidates for heredity than DNA Signup and view all the answers

What was the primary aim of Frederick Griffith's research?

To design a vaccine against bacterial pneumonia Signup and view all the answers

What did Griffith's Transformation Experiment reveal about the R strain bacteria?

They transformed into virulent bacteria when exposed to heat-treated S strain Signup and view all the answers

Which of the following best describes the 'transforming principle' identified by Griffith?

Material transferred from one strain of bacteria to another Signup and view all the answers

What led to Griffith's decision to study Streptococcus pneumoniae?

The high mortality rate from pneumococcal infections during a pandemic Signup and view all the answers

What did Griffith's research primarily use to demonstrate the transformation of bacteria?

Bacterial isolates and patient serum samples Signup and view all the answers

What tragic event occurred to Frederick Griffith in 1941?

He was killed by a German bomb Signup and view all the answers

Study Notes

DNA as the Hereditary Material: Key Experiments

DNA's Role: DNA (deoxyribonucleic acid) carries genetic information, determining traits like eye color. It was first isolated in 1869 but its role in heredity wasn't understood until later.
Early Misconceptions: Initially, scientists thought proteins, due to their abundance and complexity, were the genetic material, while believing DNA was a simple repetitive molecule.
Griffith's Transformation Experiment (1928): Griffith studied Streptococcus pneumoniae bacteria and found a "transforming principle" that could change harmless bacteria into disease-causing ones. This hinted at a transfer of genetic material.
Avery, McCarty, and MacLeod Experiment (1943): They identified the transforming principle as DNA, using a cell-free extract. This experiment directly demonstrated that DNA carried the genetic material.
Hershey-Chase Experiment (1952): This experiment used bacteriophages (viruses that infect bacteria). By labeling the phage's DNA and protein with radioactive isotopes, they showed that only the DNA entered the bacteria, proving DNA, not protein, was the genetic material that was controlling bacterial reproduction.
Conclusion: These experiments conclusively showed DNA, not protein, is the hereditary material passed on from one generation to another.

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Description

Explore the pivotal experiments that uncovered DNA's role as the hereditary material. From Griffith's initial discoveries to the confirmatory work of Avery and the Hershey-Chase experiment, learn how these studies revolutionized our understanding of genetics. This quiz will challenge your knowledge on these foundational discoveries in molecular biology.